Original description: Abathomphalus Bolli, Loeblich, and Tappan 1957: Test free, trochospiral, biconvex to concavoconvex, almost nonumbilicate, periphery with a single or double keel; sutures depressed, curved and sometimes beaded on the spiral side, depressed and radial on the umbilical side; wall calcareous, perforate, radial in structure, commonly ornamented with fine nodes, and the peripheral keels and sutures may also be beaded; primary aperture interiomarginal, extraumbilical, as a rule covered by a continuous umbihcal tegillum of irregular outline, with accessory infralaminal apertures situated at the suture contacts with the tegillum.

Distinguishing features: Test in a low to flat trochospiral, umbilicate, four to five petaloid chambers per whorl, sutures curved and oblique, depressed to thickened and nodose on the spiral side, depressed and radial around the small umbilicus on the umbilical side, periphery angular to truncate, bicarinate, the two variously spaced keels bordering an imperforate carinal band, keel on the umbilical side may be reduced to a row of short transverse costellae; wall calcareous, perforate, surface with pustules and short costellae in concentric alignment on the spiral side and radial on the umbilical side; primary aperture in teriomarginal, extraumbilical-umbilical, and with a porticus, portici of successive chambers coalescing in the early stage, larger in the adult stage and joined only at a few points to form a tegilla having distal accessory apertures.

Geological Range: Last occurrence (top): within Maastrichtian Stage (66.04-72.05Ma, top in Maastrichtian stage). Data source: Total of range of species in this databaseFirst occurrence (base): within Maastrichtian Stage (66.04-72.05Ma, base in Maastrichtian stage). Data source: Total of range of species in this database

Plot of occurrence data:

Dec 2017 - Plotting of Neptune data has been re-enabled on the Mesozoic pages following revision of the age-models in Neptune. The data is, however, still very sparse for the Early Cretaceous